1. Field of the Invention
This invention relates to compostible non-rigid absorbent structures comprising an absorbent degradable fibrous core and a backsheet that is cold water soluble and contains on both sides of the backsheet a discontinuous layer of aqueous-repellent material. A preferred species can be disposed of by toilet flushing.
2. Description of Related Art:
Landfill solid waste disposal sites are rapidly filling to capacity. A significant contribution to the landfills are absorbent batting materials, particularly diapers and feminine hygiene products. These products typically contain non-biodegradable polyolefins that do not degrade rapidly when buried.
Most municipal and septic sewage systems process solid waste by biodegradation. Therefore, the problem of overloading landfill capacity could be helped significantly if batting products were flushable, biodegradable and/or hydrolyzable and so could readily be recycled into the environment via a sewage system.
Noda U.S. Pat. No. 5,015,245 discloses disposable sanitary articles comprising a topsheet, a backsheet, and an absorbent core, wherein the backsheet is paper treated with a specific type of latex for improved wet strength. Any conventional core material can be used.
Scheckman U.S. Pat. No. 5,026,589 discloses disposable sanitary garments comprising top and/or back sheets prepared from polymers based on dioxanone.
Ells U.S. Pat. No. 3,683,919 discloses a flushable sanitary napkin comprising an absorbable cellulosic fibrous core, between a topsheet and a backsheet that can be torn apart and separated from the core for flushing. The top and backsheets may be biodegradable or not, but can be processed through municipal and septic sewer systems. This product has the disadvantage that before flushing the top and backsheets must be torn apart to expose the cellulose core to the sewage system.
Morgan U.S. Pat. No. 2,999,788 discloses the manufacture of highly branched discontinuous fibrils by a spurting technique.
Clendening U.S. Pat. No. 3,844,987 discloses relatively non-absorbable rigid seed germination containers made from naturally occurring biodegradable material such as wood pulp bonded by a biodegradable thermoplastic oxyalkanoyl polymer to give it strength.
Sinclair U.S. Pat. No. 4,057,537 discloses laminates made from a polyhydroxic acid (PHA), copolymer fibrous matrix which is consolidated into a rigid, non-porous laminated structure by flowing molten polymer through the fibrous material and curing it while in a mold or hydraulic press. Synthetic or natural fibers such as cellulose fibers are disclosed as the matrix.
Battelle Patent Application WO 90/01521 discloses non-porous rigid laminates made from a fibrous mat consolidated by flowing molten PHA polymer through the fibrous material and curing the polymer in a mold or hydraulic press. Fibers can include cellulose derived from wood.
Copending and commonly assigned U.S. patent application Ser. No. 07/718,938 filed Jun. 21, 1991, and now abandoned, disclose paper products comprising cellulosic fiber blended with PHA fibrous materials. The blend is heated to bond, giving a strong, liquid absorbing hydrophilic batting.
Copending and commonly assigned U.S. patent application Ser. No. 07/743,850 filed Aug. 12, 1991, discloses PHA shaped articles protected against premature degradation by one or more surfaces being coated with a discontinuous layer of hydrophobic and/or oleophobic material that will repel degrading liquids.
Totally degradable polymers are being used more frequently in health care products. Webb U.S. Pat. No. 4,900,299 discloses a biodegradable tampon applicator with a molded, hollow cylindrical body of a moldable degradable poly-3-hydroxybutyric acid composition.
Espy U.S. Pat. No. 4,458,042 describes improved absorbent materials formed by blending wood fluff pulp and spurted polyolefin pulp which has been treated with a wetting agent substance, and then heating the blend at a temperature for a time sufficient to consolidate the treated spurted polyolefin pulp.
Cellulosic products bonded with polyolefins do not degrade as rapidly, or completely, as cellulosic products bonded with poly(hydroxy acid) (PHA) polymers. Carl Lehrburger, author of a reusable diaper industry funded report titled "Diapers In The Waste Stream", suggests a design change. "The only biodegradable diaper may be the two piece diaper with a reusable cover and a flushable pad", his report says "However, this is not commercially available or feasible at this time." (Nonwovens Industry, October 1989, Pg. 24).